decay
This word carries a heavy scent of biological breakdown and inevitable loss. It evokes the image of organic matter returning to the earth or a structure slowly crumbling under the weight of time and neglect. There is a persistent feeling of entropy and the irreversible transition from a state of wholeness to a state of ruin. In social or moral contexts, it describes a slow, systemic collapse rather than a sudden crash. When applied to a society or a person's character, it suggests a creeping rot from within, where the core strength is eaten away until the entire system becomes unstable and fragile.
Countable when referring to a specific instance of rot, such as a cavity in a tooth. Uncountable when referring to the general scientific process of decomposition.